This invention relates to a surgical instrument, and in particular to adjustable arthroscopic surgical instruments.
Arthroscopic surgical instruments typically include a rigid outer tube within which a rigid inner tube is rotated by a motor. A cutting implement, such as a blade or abrading burr, is disposed on the distal end of the inner tube. Tissue or bone is exposed to the cutting implement through an opening in the distal end of the outer tube, and tissue or bone fragments cut by the rotating blade or burr are drawn through the interior of the inner tube along with irrigating fluid by the use of suction applied at the proximal end of the instrument. Examples of such surgical instruments are described in U.S. Pat. No. 4,203,444--Bonnell et al.; U.S. Pat. No. 4,274,414--Johnson et al.; and U.S. Pat. No. 4,842,578--Johnson et al.
The aforesaid typical arthroscopic surgical instruments are linear, or in other words, straight between their proximal and distal ends. Such linear or straight instruments have limitations and disadvantages in many surgical operations, as most body parts and cavities of humans and animals are not straight, but have curved and/or irregular surfaces. It has been recognized that it is sometimes useful for such instruments to be curved to facilitate positioning the cutting implement against the tissue, bone or cartilage to be cut.
Accordingly, more recently, arthroscopic surgical instruments have been developed which have a fixed bend or curve placed in the rigid outer tube at the time of fabrication of the instrument. Examples of such instruments with such fixed bends or curves in the rigid outer tube are described in U.S. Pat. No. 4,646,738--Trott and U.S. Pat. No. 5,152,744--Krause et al. Both of these patents disclose a rigid outer tube with a predetermined bend therein which is placed and fixed in the instrument at the time of fabrication of the instrument. At least a portion of the inner tube for transmitting torque to the cutting blade is made flexible such that it freely rotates within the bend in the outer rigid tube.